A recent study on adsorption of metolachlor on activated carbons carried out by Gomis-Berenguer et al. has reported higher adsorption capacity for pure S-metolachlor compared with the adsorption capacity for the racemic mixture of this pesticide. The authors claim that the adsorption is enantioselective, with the activated carbon being more efficient for the adsorption of the S enantiomer compared with the R enantiomer. In this comment, we question this explanation (since the non-chiral surface of an activated carbon would never be selective towards one enantiomer instead of the other) and we offer some possible answers supported by theoretical calculations.
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